In a known method of making a light-emitting diode, several epitaxial layers, on which a bond pad is formed, are formed on a growth substrate. The epitaxial layers include an n-type semiconductor layer, a p-type semiconductor layer, and an active layer between the n-type semiconductor layer and the p-type semiconductor layer. The electrons and the holes recombine to emit light provided the active layer is under a bias voltage. The active layer can be classified into categories including as single heterostructure (SH), double heterostructure (DH), double-side double heterostructure (DDH), and multi-quantum well (MQW) etc. The epitaxial layers are formed by chemical vapor deposition (CVD) or physical vapor deposition (PVD).
The bond pads usually electrically connect to the n-type and p-type semiconductor layers by wire-bonding or flip-chip. Therefore, metal is chosen to be the material of the bond pad in principle because it can bear the impact of wire-bonding when the thickness is sufficient. In general, the bond pads are formed on a wafer settled on a spinner by metal deposition. Owing to the omni-directional characteristic of deposition, the material tends to cover the area not designated for the bond pad, and then needs to be removed. From the top view of a chip, the bond pad occupies only 10%˜20% of the chip area. In other words, the material covering 80%˜90% of the chip area, the spinner, and the chamber of the equipment is redundant and needs to be removed. Even we recycle the redundant material, only 50%˜70% of it can be recycled.